JP6722281B2 - Beam shaper used for neutron capture therapy - Google Patents

Description

The present invention relates to a beam shaper, and more particularly to a beam shaper used for neutron capture therapy.

With the development of atomic science, radiation therapy such as Cobalt-60, linac and electron beam has already become one of the main means of cancer treatment. However, conventional photon or electron therapy kills tumor cells by limiting the physical conditions of the radiation itself and damages many normal tissues in the beam path. Moreover, the degree of sensitivity to radiation differs depending on the tumor cells, and conventional radiation therapy has a therapeutic effect on highly radiation-resistant malignant tumors (eg, glioblastoma multiforme, melanoma). Is not good.

Targeted therapies in chemotherapy have been used for radiation therapy to reduce radiation damage to normal tissue surrounding the tumor. In addition, radiation sources with high relative biological effectiveness (RBE) are currently being actively developed for tumor cells with high radiation resistance (eg, proton beam therapy, heavy particle therapy, neutron capture). Therapy etc.). Of these, neutron capture therapy is a combination of the above two concepts. For example, in boron neutron capture therapy, boron-containing drugs specifically collect in tumor cells and, combined with high precision neutron beam control, offer better cancer treatment options compared to conventional radiation.

Boron Neutron Capture Therapy (BNCT) takes advantage of the characteristic that a drug containing boron ( ¹⁰ B) has a large capture cross section for thermal neutrons, and captures ¹⁰ B(n,α) ⁷ Li neutrons and fission reactions. Produces two types of heavy charged particles, ⁴ He and ⁷ Li. Figure 1 and Figure 2 show the reaction scheme for boron neutron capture and the nuclear reaction equation for ¹⁰ B(n,α) ⁷ Li neutron capture, respectively. The two types of heavy charged particles have an average energy of 2.33 MeV, and are characterized by high linear energy transfer (LET) and short range. The linear energy application and range of α particles are 150 keV/μm and 8 μm, respectively, and in case of ⁷ Li heavy particles, they are 175 keV/μm and 5 μm, respectively. Since the total range of the two types of particles is close to the size of cells, radiation damage to the living body can be suppressed to the level of cells. By selectively collecting the boron-containing drug in the tumor cells and combining it with an appropriate neutron source, the tumor cells can be partially killed without significant damage to normal tissue.

The effect of boron neutron capture therapy is also called two-dimensional binary cancer therapy because it depends on the concentration of the boron-containing drug and the number of thermal neutrons at a certain site of the tumor cell. In view of this, in addition to the development of boron-containing drugs, improving the radiant flux and quality of neutron sources is also very important for the study of boron neutron capture therapy.

However, the prior art boron neutron capture therapy beam shaper design is mostly a fixed structure, and the quality of the neutron beam output from such a beam shaper is often fixed, but the actual treatment In the process, the requirements for neutron beam quality are not uniform. Different patients may have different tumor locations, depths and tumor types, which poses different requirements on the quality of the neutron beam during the course of treatment. However, the conventional fixed beam shaping body of the prior art cannot adjust the quality of the neutron beam based on the specific situation of the patient's tumor and treat according to the actual situation of the patient.

Therefore, there is a need to provide a new technical solution to the above problems.

In order to solve the above, one aspect of the present invention provides a beam forming body used for neutron capture therapy. The beam shaper includes a beam entrance, a target, a moderator adjacent to the target, a reflector surrounding the moderator, and a beam exit, and the target causes a nuclear reaction with a proton beam incident from the beam entrance. Generates neutrons, the moderator slows down neutrons generated from the target, the reflector returns the deviated neutrons to the moderator to improve the beam intensity of epithermal neutrons, and the moderator is replaced. Adjust the neutron moderating ability of the moderator.

Further, the moderator includes a base part located behind the target and an expansion part provided separately from the base part, and the expansion part is independently replaced to adjust the neutron moderating ability of the moderator.

Further, the base portion is adjacent to the rear of the target and is fixed to the target, and the extension portion is attached to the rear of the base portion and is adjacent to the base portion.
Further, the expansion part includes at least a first expansion part and a second expansion part, the first expansion part is attached to the rear of the base part and is adjacent to the base part, and the second expansion part is the first expansion part. The first expansion part and the second expansion part are mounted rearward and adjacent to the first expansion part, and the first expansion part and the second expansion part can be independently replaced.

A guide groove is provided on the reflector so as to extend to the rear of the base portion corresponding to the extension portion, and a slide rail is provided in the guide groove. After the expansion part is mounted in the guide groove, it is moved to the rear of the base part by the slide rail and is adjacent to the base part. The guide groove includes at least a first guide groove corresponding to the first expanded portion and a second guide groove corresponding to the second expanded portion. When the structural dimensions of the first expansion portion and the second expansion portion are the same and only the materials are different, the first expansion portion and the second expansion portion can be installed in the first guide groove or the second guide groove, respectively. .. When the structural dimensions of the first expansion part and the second expansion part are different and the materials are also different, the first expansion part is installed in the first guide groove, and the second expansion part is installed in the second guide groove.

Further, the reflector includes auxiliary reflectors provided on both outer sides of the extension part and mounted in the guide groove, and when the extension part is attached to the rear of the base part by the slide rails, the auxiliary reflector and the outside of the base part. The reflectors surrounding the jointly reflect the scattered neutrons.

Further, the reflector is provided with a rotation shaft, and the rotation shaft is provided with a turntable located behind the base portion and rotatable with respect to the base portion. After the expansion part is mounted in the turntable, the extension part is rotated rearward of the base part together with the turntable to be adjacent to the base part. The turntable includes at least a first turntable corresponding to the first extension and a second turntable corresponding to the second extension. When the structural dimensions of the first expansion portion and the second expansion portion are the same and only the materials are different, the first expansion portion and the second expansion portion can be mounted on the first rotary disk or the second rotary disk, respectively. When the structural dimensions of the first expansion part and the second expansion part are different and the materials are also different, the first expansion part is mounted on the first rotary disk, and the second expansion part is mounted on the second rotary disk. It

Further, the reflector further includes an auxiliary reflector provided on the outer periphery of the extension part, and when the extension part is rotated around the rotation axis and mounted behind the base part, the auxiliary reflector and the outside of the base part are removed. The surrounding reflectors jointly reflect the scattered neutrons.

Further, the materials of the base portion, the first extension portion, and the second extension portion are all Al, Pb, Ti, Bi, C, D ₂ O, AlF ₃ , fluental, CaF ₂ , Li ₂ CO ₃ , MgF. ₂ and any one or more of Al ₂ O ₃ can be produced.

Further, the reflector is made of at least one of Pb and Ni, and the material of the auxiliary reflector is the same as the material of the reflector.
Compared with the prior art, the present application has the following beneficial effects. The beam forming body used in the neutron capture therapy of the present application is to design a moderator consisting of a base part and an expanding part, and set the expanding part as two replaceable parts. Depending on the specific medical condition of the patient (the depth of the tumor in the patient), the moderator can slow down the neutron beam by selecting and replacing different material extensions, so the patient actually needs it during treatment. The quality of the neutron beam can be obtained, the structure is simple, and the application is flexible.

It is a reaction schematic diagram of a boron neutron capture. It is a structural diagram of the beam shaping body used for neutron capture therapy. FIG. 6 is a structural diagram in which an extension portion is mounted using the guide groove of the first embodiment of the present invention. It is a structural diagram which attached the expansion part using the turntable of 2nd Embodiment of this invention.

In recent years, neutron capture therapy has been increasingly applied as an effective means for treating cancer, and among them, boron neutron capture therapy has become the most popular one. The neutrons used for boron neutron capture therapy can be supplied by the reactor or accelerator. Embodiments of the present invention exemplify Accelerated-based Boron Neutron Capture Therapy. The basic modules of the accelerator boron neutron capture therapy include an accelerator, a target, a heat removal system and a beam shaping assembly, which are commonly used to accelerate charged particles (protons, deuterium nuclei, etc.). Neutrons are generated by the action of the charged particles and the metal target after acceleration, the required neutron yield and energy, the energy and current of the accelerated charged particles that can be provided, and the physical and chemical characteristics of the metal target, Appropriate nuclear reactions are selected. Well-studied nuclear reactions are ⁷ Li(p,n) ⁷ Be and ⁹ Be(p,n) ⁹ B, both endothermic reactions with energy thresholds of 1.881 MeV and 2.055 MeV, respectively. Since the ideal neutron source for boron neutron capture therapy is epithermal neutrons at keV energy level, theoretically, the impact of a proton with a little higher energy than the threshold on a lithium target produces relatively low energy neutrons, and much less. Clinical application is possible without much deceleration processing. However, since the two types of targets, lithium (Li) and beryllium (Be), do not have a large cross section that interacts with protons having a threshold energy, a relatively high energy is generally required to secure sufficient neutron flux. Nuclear reaction is triggered by the protons that it has.

An ideal target has a high neutron yield, the energy distribution of the generated neutrons is close to the epithermal neutron energy region (explained in detail later), does not generate too much radiation with strong permeability, and is safe and easy. Although it is required to have characteristics such as easy operation at high temperature resistance and high temperature resistance, a lithium target is adopted in the embodiment of the present invention because a nuclear reaction that actually meets all the requirements cannot be found. However, as is well known to those skilled in the art, the target material may be any other metal material than the above metal materials.

The requirements of the heat removal system depend on the nuclear reaction chosen. For example, for ⁷ Li(p,n) ⁷ Be, the low melting point and low thermal conductivity of the metal target (lithium) makes the requirements of the heat removal system more stringent than ⁹ Be(p,n) ⁹ B. In the embodiment of the present invention, a ⁷ Li(p,n) ⁷ Be nuclear reaction is adopted.

Furthermore, in the actual course of treatment using neutron capture therapy technology, the specific situation of tumor in different patients (tumor location, depth and tumor type) may be different, and the proton and the target react with nuclear reaction. The specific requirements for the quality of the neutron beam generated after the occurrence of the neutron beam (specific range of the beam neutron energy region, neutron beam flux or neutron beam forwardness, etc.) may be different. In order to more flexibly and precisely apply the neutron capture therapy technology to the actual treatment process of tumor patients and to apply it to more kinds of tumor treatment, the present application proposes an improvement to the beam shaper used in the neutron capture therapy. .. Preferred are improvements to the beam shaper used in accelerator boron neutron capture therapy.

2 to 4 show a beam shaping body 10 used for neutron capture therapy in the present application. The beam shaping body 10 includes a beam inlet 11, a target 12, a moderator 13 adjacent to the target 12, and an outside of the moderator 13. It includes a surrounding reflector 14 and a beam exit 17. The accelerator boron neutron capture therapy accelerates a proton beam by an accelerator, and the proton beam is accelerated to an energy that overcomes the nuclear force of the target, causing a ⁷ Li(p,n) ⁷ Be nuclear reaction with the target 12 to generate neutrons. (See Figure 1). The generated neutrons are decelerated by the moderator 13, and the scattered neutrons are reflected to the beam axis through the reflector 14 and emitted from the beam exit 17.

Various materials can be used for the moderator 13. The material of the moderator 13 has a great influence on the index of the beam neutron energy region, the neutron beam flux, or the neutron beam forwardness. Therefore, in the present application, the moderator 13 is set to be replaceable, so that the neutron capture therapy cannot be performed using the same medical device for different tumor situations (including position, depth, and type). To solve.

The speed reducer 13 includes a base portion 131 and an extension portion 132, and the base portion 131 and the extension portion 132 are separate structures. The so-called separate structure is that the base portion 131 is located behind the target 12 and the extension portion 132 is mounted behind the base portion 131. The base portion 131 may be set to be replaceable or fixed. When the base part 131 is a replaceable type, the base part 131 and the extension part 132 can be respectively replaced. When the base portion 131 is fixed, only the extension portion 132 is replaced. Of course, the base portion 131 and the expansion portion 132 may be integrally provided, and the deceleration body 13 may be replaced as a whole to change the deceleration ability of the deceleration body 13 for different tumor situations.

In the present embodiment, separate design is adopted for the base portion 131 and the extension portion 132, and the base portion 131 is fixed. The base portion 131 of the speed reducer 13 is installed behind the target 12 and fixed adjacent to the target 12, and the extension portion 132 is attached behind the base portion 131 and adjacent to the base portion 131 (in other embodiments, , The extension 132 is not adjacent to the base 131, and a gap may be left between the base 131 and the extension 132). In the present embodiment, the expansion section 132 includes at least a first expansion section 133 and a second expansion section 134. The first extension 133 is adjacent to the rear of the base 131, and the second extension 134 is adjacent to the rear of the first extension 133. In this way, the expansion part 132 is formed in a laminated structure of two structures, and the first expansion part 133 and the second expansion part 134 can be independently replaced. It should be pointed out that due to the wide variety of materials from which the moderator 13 is made, the extension 132 may be configured in a stack of two or more (three, four, five or more) multiple structures. May be. As a result, the deceleration capacity of the moderator is changed more finely, so that more precise needs for the quality of the neutron beam are realized, and thereby the therapeutic effect on different tumors is improved.

Hereinafter, how to achieve replacement of the extension portion 132 of the speed reducer 13 will be specifically described.
Referring again to FIG. 3, FIG. 3 is a structural diagram of the first embodiment of the present application. The reflector 14 is provided with a guide groove 141, the guide groove 141 is provided with a slide rail 142, and the extension portion 13 slides to the rear of the base portion 132 along with the rear slide rail 142 attached to the guide groove 141. In addition, it is fixed adjacent to the base portion 132. The guide groove 141 includes a first guide groove 143 corresponding to the first expanded portion 133 and a second guide groove 144 corresponding to the second expanded portion 134. When the entire structure of the moderator 13 is a cylindrical body, and the structural dimensions of the first extension 133 and the second extension 134 are the same, the first extension of a different material depending on the quality requirement of the neutron beam to be obtained. 133 and the second expansion portion 134 may be selected and mounted in the first guide groove 143 or the second guide groove 144. That is, in such a case, since the structural dimensions of the first expansion portion 133 and the second expansion portion 134 are the same, the material of the expansion portion 132 mounted in the first guide groove 143 and the second guide groove 144 is the same. Is required to set the neutron beam quality obtained after passing through the moderator 13 to a desired condition, and either the first extension part 133 or the second extension part 134 is attached to the first guide groove 143 and the second guide groove 144. There is no limit to what you do. Quality of the neutron beam to be obtained when the entire structure of the moderator 13 is a cylinder or a cone, or a combination of a cylinder and a cone, and the structural dimensions of the first extension 133 and the second extension 134 are different. According to the requirement, the first expansion part 133 and the second expansion part 134 of different materials are selected, and the first expansion part 133 can be installed only in the first guide groove 143, and the second expansion part 134 is also compatible. It can be installed only in the second guide groove 144.

The reflector 14 further includes auxiliary reflectors 145 provided on both outer sides of the extension 131 and mounted in the guide grooves 141. The auxiliary reflector 145 may be mounted on the guide groove 141 after being manufactured integrally with the expansion portion 131, or may be mounted on the guide groove 141 independently after the expansion portion 131 is mounted on the guide groove 141. Good. When the extension 131 is attached to the rear of the base 132 by the slide rail 142, the auxiliary reflector 145 and the reflector 14 surrounding the outside of the base 131 jointly reflect scattered neutrons, As a result, the scattered neutrons are reflected by the neutron beam principal axis, further improving the beam intensity of epithermal neutrons.

Referring again to FIG. 4, FIG. 4 is a structural guide of the second embodiment of the present application. In the second embodiment, the same members as those in the second embodiment have the same reference numerals as those in the first embodiment. The reflector 14 is provided with a single rotating shaft 15 parallel to the center line of the base 131 of the speed reducer 13. The rotating shaft 15 is located behind the base 131 and rotatable relative to the base 131. A board 146 is provided. After the expansion part 132 is mounted on the turntable 146, the extension part 132 rotates together with the turntable around the rotary shaft 15 to the rear of the base part 131 and is fixed adjacent to the base part 131. The turntable 146 includes at least a first turntable 147 corresponding to the first extension 133 and a second turntable 148 corresponding to the second extension 144. When the entire structure of the moderator 13 is a cylindrical body and the structural dimensions of the first expansion portion 133 and the second expansion portion 134 are the same, the first expansion of a different material according to the quality requirement of the neutron beam to be obtained. The part 133 and the second expansion part 134 may be selected and mounted in the first rotary disk 147 or the second rotary disk 148. In such a case, since the structural dimensions of the first expanded portion 133 and the second expanded portion 134 are the same, the material of the expanded portion 132 mounted on the first rotary disk 147 and the second rotary disk 148 is The quality of the neutron beam obtained after passing through the moderator 13 can be set to a desired condition, and which of the first extension part 133 and the second extension part 134 is attached to the first turntable 147 and the second turntable 148. There is no request for. When the entire structure of the moderator 13 is a cylindrical body, or a cone, or a combination of a cylindrical body and a cone, and the structural dimensions of the first extension 133 and the second extension 134 are different, the quality requirement of the neutron beam to be obtained must be satisfied. Accordingly, the first expansion part 133 and the second expansion part 134 of different materials are selected, and the first expansion part 133 correspondingly only attaches to the first turntable 147, and the second expansion part 134 also corresponds to the first expansion part 133. Can be installed only on the two-turn table 148.

The reflector 14 further includes an auxiliary reflector 145 ′ provided on the outer periphery of the extension 132. The auxiliary reflector 145′ may be mounted in the turntable 146 after being manufactured integrally with the extension 132, or may be independently attached to the turntable 146 after the extension 131 is attached to the turntable 146. Good. When the extension 132 rotates around the rotation axis Z and is mounted behind the base 131, the auxiliary reflector 145 ′ and the reflector 14 surrounding the outside of the base 131 cooperate with each other for scattered neutrons. The reflected neutrons are reflected by the main axis of the neutron beam, thereby improving the beam intensity of epithermal neutrons.

The moderator 13 is made of a material having a wide fast neutron action cross section and a narrow epithermal neutron action cross section. Preferably, the moderator 13 is made of at least one of Al, Pb, Ti, Bi, C, D ₂ O, AlF ₃ , fluental, CaF ₂ , Li ₂ CO ₃ , MgF ₂ and Al ₂ O _3. .. To explain further, the base portion 131 of the moderator 13 includes at least one of Al, Pb, Ti, Bi, C, D ₂ O, AlF ₃ , fluental, CaF ₂ , Li ₂ CO ₃ , MgF ₂ and Al ₂ O 3. or manufactured in a wide, the material of the first extended portion 133 and second extended portion 134 also, Al, Pb, Ti, Bi , C, D 2 0, AlF 3, _{Furuentaru, CaF 2, Li 2 CO 3} , MgF 2 And at least one or more of Al ₂ O ₃ . That is, in the present application, the materials of the first expansion portion 133, the second expansion portion 134, and the base portion 131 may match each other or may differ from each other. The reflector 14 is made of a material having excellent neutron reflection ability, and in a preferred embodiment, the reflector 14 is made of at least one of Pb and Ni.

Further, an epithermal neutron absorber (not shown) may be provided at the rear end of the moderator 13, a gap passage 18 is provided between the moderator 13 and the reflector 14, and the epithermal neutron absorber and the beam An air passage 19 is provided between the outlets 17 and a radiation shield 16 is provided within the reflector 14 which can reduce the normal tissue dose in the non-irradiated areas. The so-called gap passage 18 is a region where a hollow neutron beam that is not covered with a substance is easily passed, and the gap passage 18 may be provided as an air passage or a vacuum passage. By providing the clearance passage 18, the flux of epithermal neutrons can be increased, and by providing the air passage 19, neutrons deviating from the main axis of the neutron beam are continuously returned to the main axis, and the epithermal neutron beam The strength can be increased. The radiation shield 16 includes a photon shield 161 for blocking leaking photons in the neutron beam and a neutron shield 162 for blocking leaking neutrons in the neutron beam. The photon shield 161 may be provided integrally with the reflector 14 or may be provided separately, and the neutron shield 162 may be provided at a position adjacent to the beam exit 17.

The proton beam is injected from the beam inlet 11 and undergoes a nuclear reaction with the target 12 to generate neutrons. The neutrons form a neutron beam, and the neutron beam is limited to one beam main axis. 13. The neutrons are decelerated by 13 to the epithermal neutron energy region and the thermal neutron absorber absorbs thermal neutrons in the neutron beam, thereby avoiding excessive doses to shallow normal tissue during treatment. The reflector 14 returns neutrons that deviate from the beam principal axis back to the beam principal axis to enhance the beam intensity of epithermal neutrons, thereby obtaining a beam quality that best matches the treatment of the patient.

The thermal neutron absorber is made of a material having a wide action cross section of thermal neutrons, and in a preferred embodiment, the thermal neutron absorber is made of ⁶ Li. Preferably, lead (Pb) is selected as the material of the photon shield 161, and polyethylene (PE) is selected as the material of the neutron shield. As is well known to those skilled in the art, the photon shield 161 may be made of another material as long as it can act to shield photons, and the neutron shield 162 may be made of another material. It may be set at another place as long as the condition for shielding leaked neutrons is satisfied.

The beam shaping body of the neutron capture therapy of the present application is the same as the moderating ability for neutrons by selecting moderators of different materials according to the actual requirements for the tumor beam neutron energy region, neutron beam flux, etc. The medical device can treat different patients, has a simple structure and is suitable for use.

The beam shaping assembly for neutron capture therapy disclosed by the present invention is not limited to the contents described in the above embodiments and the structures shown in the drawings. Any obvious changes, substitutions or modifications in the material, shape and position of the components disclosed herein based on this application are within the scope of protection of the claims of the present invention.

Claims (7)

A beam shaper used for neutron capture therapy,
The beam shaper includes a beam entrance, a target, a moderator adjacent to the target, a reflector surrounding the moderator, and a beam exit. The target interacts with a proton beam incident from the beam entrance. Wake to generate neutrons, the moderator slows down neutrons generated from the target, the reflector returns the deviated neutrons to the moderator to improve the beam intensity of epithermal neutrons, and the moderator is replaced. It is to adjust the deceleration capability for neutrons moderator,
The moderator includes a base part located behind the target, and an expansion part provided separately from the base part, and the expansion part is independently replaced to adjust the moderating ability of the moderator against neutrons. ,
The reflector includes a guide groove extending to the rear of the base portion corresponding to the expansion portion, and an auxiliary reflector provided on both outer sides of the expansion portion and mounted in the guide groove,
The auxiliary reflector and the reflector surrounding the outside of the base portion jointly reflect scattered neutrons,
Beam shaper used for neutron capture therapy. The base part is adjacent to the rear of the target and is fixed to the target, and the expansion part is attached to the rear of the base part and is adjacent to the base part.
A beam shaper used in the neutron capture therapy according to claim 1 . The expansion part includes at least a first expansion part and a second expansion part, the first expansion part is attached to the rear of the base part and is adjacent to the base part, and the second expansion part is behind the first expansion part. It is mounted and adjacent to the first expansion part, and the first expansion part and the second expansion part are independently replaceable,
A beam shaper used in the neutron capture therapy according to claim 1 . Slide rail is provided on the front Symbol guide groove, wherein the extension, after being fitted in the guide groove, adjacent to the base portion to move to the rear of the base portion by the slide rails,
The guide groove includes at least a first guide groove corresponding to the first expanded portion and a second guide groove corresponding to the second expanded portion,
When the structural dimensions of the first expansion portion and the second expansion portion are the same and the materials are different, the first expansion portion and the second expansion portion are mounted in the first guide groove or the second guide groove, respectively. Can
When the structural dimensions of the first expansion part and the second expansion part are different and the materials are also different, the first expansion part is mounted in the first guide groove, and the second expansion part is mounted in the second guide groove. ,
Characterized by that
A beam shaper used in the neutron capture therapy according to claim 3 . When extension unit is attached to the rear of the base portion by the slide rail, the reflector surrounding the outside of the auxiliary reflector and the base portion is characterized by reflecting jointly neutron scattering,
A beam shaper used in the neutron capture therapy according to claim 4 . The base portion, the material of the first extension and the second extension portion are all, Al, Pb, Ti, Bi , C, D2O, AlF3, Furuentaru, CaF2, Li2 CO3, any kind in the MgF2 and Al2O3 or characterized that you have been prepared granulated in a wide,
A beam shaper used in the neutron capture therapy according to claim 3. The reflector is made of at least one of Pb and Ni, and the material of the auxiliary reflector is the same as the material of the reflector.
A beam shaper used for the neutron capture therapy according to any one of claims 1 to 6 .

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